چكيده به لاتين
The primary purpose of this thesis is to investigate the sound transmission loss (STL) on a doubly curved Shell with the three-dimensional auxetic honeycomb core. First, the modeling of a doubly curved shell has been presented by the state vector method with applying the theory of three-dimensional elasticity. Accordingly, by calculating the local transfer matrix in a sub-layer and then obtaining the general transfer matrix for all layers, the relationship between all the layers formed in the state vector method has been acquired. In the next step, the elastic properties of the 3D auxetic honeycomb core used to reduce the weight of structures as core, have been obtained including, Young's modulus, shear modulus, and Poisson's ratio in three directions. Next, the multilayered process of the structure, which consists of two doubly curved shells with a core, has been performed. Then, by applying the boundary conditions, the eight unknowns have been calculated, and finally, a relation has been obtained to calculate the sound transmission loss. To validate the problem, the results have been compared with those of other studies, and excellent agreement has been specified. In the end, the effects of different doubly curved shell and core parameters on the STL have been studied. The results have been shown that increasing the curvature of the structure enhances the stiffness of the structure, which this parameter significantly increases the STL in the stiffness control domain. Also, accordingly, the crucial substantial effect of embedding the core has been to reduce the amount of curvature frequency and in other parts of the stiffness control domain does not have a significant effect. However, in the mass control domain, adding the core into the structure has a significant effect on the increase of STL and increase the value of coincidence frequency.
